I like the Iwama style for its simplicity and feel. One major difference is that this style of bokken is generally not used with a tsuba. I've been told that this is because the styles that generally use this bokken feel that not having a tsuba forces the user to have more precise technique. So , in other words, if your technique is sloppy, your knuckles get smashed. However, although the shape of the Iwama bokken is not ideally suited for a tsuba, I retrofitted a plastic one that does stay on mine.
Hope this helps a bit.
Steve